Spatial Filtering with Nonlocal Non-Hermitian Metasurfaces

Abstract

Spatial filtering of optical fields has widespread applications ranging from beam shaping to optical information processing. However, conventional spatial filters are bulky and alignment-sensitive. Here, we present nonlocal non-Hermitian metasurfaces that can act as exceptionally effective optical spatial filters while being highly compact and insensitive to both lateral and longitudinal displacements. The metasurface design is based on a resonant waveguide grating in which radiative losses of the modes are tailored to realize a symmetry-protected bound state in the continuum in the middle of a non-Hermitian flat band. Using this design, we propose a compact spatial filtering device operating over an angular range of approximately 1 degree around normal incidence. In addition to being ultrathin and robust against translational misalignment, the proposed metasurfaces are easy to manufacture, which makes them an attractive alternative to conventional spatial filters, holding a potential to become a widely used optical component.

9 pages, 9 figures

References in corpus (19)

• Edge states and topological invariants of non-Hermitian systems
• All-optical signal processing platforms for CMOS compatible integrated nonlinear optics
• Topological Origin of Non-Hermitian Skin Effects
• Topological nature of bound states in the radiation continuum
• Spawning rings of exceptional points out of Dirac cones
• Applications of Bound States in the Continuum in Photonics
• Probing non-Hermitian Skin Effect and non-Bloch Phase Transitions
• Selection Rules for Quasi-Bound States in the Continuum
• Nonlocal Flat Optics
• Minireview on Disordered Optical Metasurfaces
• Exceptional contours and band structure design in parity-time symmetric photonic crystals
• Observation of enhanced free-electron radiation from photonic flatband resonances
• Polarization Imaging and Edge Detection with Image-Processing Metasurfaces
• Dispersion Engineered Metasurfaces for Broadband, High-NA, High-Efficiency, Dual-Polarization Analog Image Processing
• Photonic time crystals: Theory and applications
• Perfect diffraction metagratings supporting bound states in the continuum and exceptional points
• Quantum interference and exceptional points
• Enabling infinite $Q$ factors in absorbing optical systems
• Recovery of topologically robust merging bound states in the continuum in photonic structures with broken symmetry